Root Name Server + TLD Server

Im doing an assignment for DNS on Ubuntu 10 using BIND9. Everything is on an internal network with private IP addresses and not access to the internet.
I have set up my own root name server (.) and a top level domain server (com). I also have another server configured for example.com. In the root name server's zone file I have the A record for the TLD server (com) and when I do "nslookup com" I get the address of the root name server and then the correct address of the com server. When I do "nslookup example.com" I get the output "server cant find example.com: NXDOMAIN".

What I want to do is when I do "nslookup example.com" I want it to return the IP address of the top level domain (com) server. I dont want to include the A record of example.com in the root zone file because then it will give me the address of example.com and not com. Can any please tell me how I can do this?

It's working how it should. In your config, example.com does not exist. So it returns NXDOMAIN. Tagged along with an NXDOMAIN response should normally be the root SOA record as well. I would also suggest using dig instead of nslookup. You'll probably be better off in interpreting and troubleshooting responses.